Time filter

Source Type

Vasantha T.,Sri Padmavathi Womens Degree and Post Graduate College | Kumar A.,University of Delhi | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College
Protein and Peptide Letters | Year: 2014

In recent years, ionic liquids (ILs) represent a new class of biocompatible co-solvents for biomolecules. In this work, we report the apparent transfer free energies (ΔG′tr) for six amino acids (AA) from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG′ tr for AA from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the obtained results, we found that the selected ammonium based ILs act as stabilizers for the structure of AA. © 2014 Bentham Science Publishers.


Vasantha T.,Sri Padmavathi Womens Degree and Post Graduate College | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Devi R.S.R.,Sri Padmavathi Womens Degree and Post Graduate College
Journal of Physical Chemistry B | Year: 2012

Protein folding/unfolding is a fascinating study in the presence of cosolvents, which protect/disrupt the native structure of protein, respectively. The structure and stability of proteins and their functional groups may be modulated by the addition of cosolvents. Ionic liquids (ILs) are finding a vast array of applications as novel cosolvents for a wide variety of biochemical processes that include protein folding. Here, the systematic and quantitative apparent transfer free energies (δ G′tr) of protein model compounds from water to ILs through solubility measurements as a function of IL concentration at 25 °C have been exploited to quantify and interpret biomolecular interactions between model compounds of glycine peptides (GPs) with ammonium based ILs. The investigated aqueous systems consist of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly2), triglycine (Gly3), tetraglycine (Gly4), and cyclic glycylglycine (c(GG)) in the presence of six ILs such as diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA). We have observed positive values of δ G′tr for GPs from water to ILs, indicating that interactions between ILs and GPs are unfavorable, which leads to stabilization of the structure of model protein compounds. Moreover, our experimental data δ G′tr is used to obtain transfer free energies (δ g′tr) of the peptide backbone unit (or glycyl unit) (-CH 2C=ONH-), which is the most numerous group in globular proteins, from water to IL solutions. To obtain the mechanism events of the ILs' role in enhancing the stability of the model compounds, we have further obtained m-values for GPs from solubility limits. These results explicitly elucidate that all alkyl ammonium ILs act as stabilizers for model compounds through the exclusion of ILs from model compounds of proteins and also reflect the effect of alkyl chain on the stability of protein model compounds. © 2012 American Chemical Society.


Kavitha T.,Sri Padmavathi Womens Degree and Post Graduate College | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Devi R.S.R.,Sri Padmavathi Womens Degree and Post Graduate College | Hofman T.,Warsaw University of Technology
Journal of Physical Chemistry B | Year: 2012

Mixing of ionic liquids (ILs) with molecular solvent can expand the range of structural properties and the scope of molecular interactions between the molecules of the solvents. Exploiting of these phenomena essentially require a basic fundamental understanding of mixing behavior of ILs with molecular solvents. In this context, a series of protic ILs possessing tetra-alkyl ammonium cation [R4N]+ with commonly used anion hydroxide [OH]- were synthesized and characterized by temperature dependent thermophysical properties. The ILs [R4N]+[OH]- are varying only in the length of alkyl chain (R is methyl, ethyl, propyl, or butyl) of tetra-alkyl ammonium on the cationic part. The ILs used for the present study included tetramethyl ammonium hydroxide [(CH3) 4N]+[OH]- (TMAH), tetraethyl ammonium hydroxide [(C2H5)4N]+[OH]- (TEAH), tetrapropyl ammonium hydroxide [(C3H7)4N] +[OH]- (TPAH) and tetrabutyl ammonium hydroxide [(C 4H9)4N]+[OH]- (TBAH). The alkyl chain length effect has been analyzed by precise measurements such as densities (ρ), ultrasonic sound velocity (u), and viscosity (η) of these ILs with polar solvent, N-methyl-2-pyrrolidone (NMP), over the full composition range as a function of temperature. The excess molar volume (VE), the deviation in isentropic compressibility (Δκs) and deviation in viscosity (Δη) were predicted using these properties as a function of the concentration of ILs. Redlich-Kister polynomial was used to correlate the results. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and NMP molecules. Later, the hydrogen bonding features between ILs and NMP were also analyzed using a molecular modeling program with the help of HyperChem 7. © 2012 American Chemical Society.


Vasantha T.,Sri Padmavathi Womens Degree and Post Graduate College | Kumar A.,University of Delhi | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College
Fluid Phase Equilibria | Year: 2012

Understanding the folding process of proteins or polypeptides in co-solvents is a fascinating and critical issue in biophysical chemistry. In recent years, ionic liquids (ILs) represent a versatility of the new class of co-solvents. To quantify the bimolecular interactions of amino acids (AA), such as l-alanine (Ala) and l-valine (Val) with biocompatible ILs, we report the apparent transfer free energies (ΔG'tr) for AA from water to aqueous solutions of six ammonium based ILs (diethylammonium acetate (DEAA), diethylammonium sulfate (DEAS), triethyl ammonium acetate (TEAA), triethylammonium sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA)) through solubility measurements, as a function of IL concentration at 298.15. K under atmospheric pressure. Salting-out effect was found for AA in aqueous IL solutions with increasing IL concentrations. In addition, we observed positive values of ΔG'tr for Ala and Val from water to ILs, indicating that the interactions between ILs and AA are unfavorable. From the solubility results, we envisage that the selected ammonium based-ILs provide stability to the structure of AA. Further, the stability of AA has been studied by means of the UV-vis spectroscopy. © 2012 Elsevier B.V.


Vasantha T.,Sri Padmavathi Womens Degree and Post Graduate College | Kavitha T.,Sri Padmavathi Womens Degree and Post Graduate College | Kumar A.,University of Delhi | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College
Journal of Molecular Liquids | Year: 2015

The interactions between ionic liquids (ILs) and amino acids (AAs) can easily be quantified using the apparent transfer free energy (δG′tr) values that can be used to interpret the stability of the proteins in the same solvent medium. In this study, δG′tr values of AAs such as phenylalanine (Phe), histidine (His), threonine (Thr), glutamine (Gln) and serine (Ser) from the water to ILs have been obtained from the solubility measurements, as a function of IL concentration at 298.15 K under atmospheric pressure. The investigated ILs contain diethylammonium acetate (DEAA), diethylammonium hydrogen sulfate (DEAS), triethylammonium acetate (TEAA), triethylammonium hydrogen sulfate (TEAS), triethylammonium dihydrogen phosphate (TEAP), and trimethylammonium acetate (TMAA). The results reveal that the IL effect was specific and independent for each AA in the aqueous medium. Apparently, we observed a positive as well as negative δG′tr values for Phe, His, Glu, Thr, and Ser AAs in the ammonium-based ILs. © 2015 Elsevier B.V. All rights reserved.


Kavitha T.,Sri Padmavathi Womens Degree and Post Graduate College | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College | Hofman T.,Warsaw University of Technology
Thermochimica Acta | Year: 2012

To address the molecular interactions between ionic liquids (ILs) such as trimethylammonium acetate [(CH 3) 3NH][CH 3COO] (TMAA), trimethylammonium hydrogen sulphate [(CH 3) 3NH][HSO 4] (TMAS), trimethylammonium dihydrogen phosphate [(CH 3) 3NH][H 2PO 4] (TMAP) and triethylammonium dihydrogen phosphate [(CH 3CH 2) 3NH][H 2PO 4] (TEAP) with N-methyl-2-pyrrolidone (NMP), density (ρ), ultrasonic sound velocity (u) and viscosity (η) measurements have been performed across the entire concentration range and the wide temperature range from 298.15 to 313.15 K in steps of 5 K under ambient pressure. Further, on the basis of the measured properties, excess volumes (V E), isentropic compressibility deviations (Δκ s) and viscosity deviations (Δη) were obtained for all these systems under the same experimental conditions. The results are correlated by the Redlich-Kister type equation. The results are also analysed on anion dependent phenomena and temperature influence on measured and derived properties of ILs with NMP mixtures. A qualitative analysis of molecular interactions between ILs and NMP is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding. © 2012 Elsevier B.V. All rights reserved.


Kavitha T.,Sri Padmavathi Womens Degree and Post Graduate College | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College | Hofman T.,Warsaw University of Technology
Journal of Chemical Thermodynamics | Year: 2012

We report the synthesis and characterisation of a series of ammonium ionic liquids (ILs) containing acetate and sulphate anions with alkyl ammonium cation. To understand the thermophysical properties of these synthesised ILs with polar solvent N-methyl-2-pyrrolidone (NMP), precise measurements such as densities (ρ), speed of sound (u), and viscosity (η) over the entire mole fraction range have been measured at 5 K intervals within the temperature range of (298.15 to 313.15) K under atmospheric pressure. The excess molar volume (V E), the deviation in isentropic compressibility (Δκ s), and deviation in viscosity (Δη) were predicted using these temperature dependence properties as a function of the concentration of ILs. The Redlich-Kister polynomial was used to correlate the results. The ILs investigated in the present work included diethylammonium acetate (DEAA) [(CH 3CH 2) 2NH][CH 3COO], triethylammonium acetate (TEAA) [(CH 3CH 2) 3NH][CH 3COO], diethylammonium hydrogen sulphate (DEAS) [(CH 3CH 2) 2NH][HSO 4], and triethylammonium hydrogen sulphate (TEAS) [(CH 3CH 2) 3NH][HSO 4]. The intermolecular interactions and structural effects were analysed on the basis of the measured and the derived properties. The information reported here in terms of ion-dipole interactions, ion-pair interactions and hydrogen bonding between ILs and NMP, elucidates the influences of ions and also the temperature effects on the thermophysical properties. © 2012 Elsevier Ltd. All rights reserved.


Kavitha T.,Sri Padmavathi Womens Degree and Post Graduate College | Vasantha T.,Sri Padmavathi Womens Degree and Post Graduate College | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College | Hofman T.,Warsaw University of Technology
Journal of Molecular Liquids | Year: 2014

This work presents the thermophysical properties and structure of N-methyl-2-pyrrolidone (NMP) in the binary mixtures with 1-alkyl-3-methyl imidazolium cation [amim]+ with different anions (chloride, methyl sulfate and tetrafluoroborate) of ionic liquids (ILs). A comprehensive set of properties such as densities (ρ), ultrasonic sound velocities (u) and viscosities (η) have been measured at the temperature range from 298.15 to 313.15 K over the whole concentration range of ILs under atmospheric pressure. The ILs used for the present study included 1-ethyl-3-methylimidazolium methylsulfate [Emim][MeSO4], 1-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF4], 1-ethyl-3-methyl imidazolium chloride [Emim][Cl] and 1-butyl-3-methylimidazolium chloride [Bmim][Cl] from imidazolium family of ILs. From these experimental data, the excess molar volume (V E), the deviation in isentropic compressibility (Δκ s) and deviation in viscosity (Δη) were calculated and adequately correlated by using the Redlich-Kister polynomial equation. The measured and calculated data were interpreted on the basis of intermolecular interactions and structural effects between like and unlike molecules upon mixing. © 2014 Elsevier B.V.


Vasantha T.,Sri Padmavathi Womens Degree and Post Graduate College | Attri P.,University of Delhi | Venkatesu P.,University of Delhi | Rama Devi R.S.,Sri Padmavathi Womens Degree and Post Graduate College
Journal of Chemical Thermodynamics | Year: 2012

To quantify the biomolecular interactions of protein functional groups with biocompatible ionic liquids (ILs), transfer free energies (ΔGtr′) of model compounds from water to aqueous ILs solutions have been determined from the solubility measurements, as a function of ILs concentration at T = 298.15 K under atmospheric pressure. The aqueous systems investigated contain amino acids of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly 2), and cyclic glycylglycine (c(GG)) with ILs of diethylammonium acetate ([Et 2NH][CH 3COO], DEAA), triethylammonium acetate ([Et 3NH][CH 3COO], TEAA), and trimethylammonium acetate ([Me 3NH][CH 3COO], TMAA). It was found that the solubility of model compounds in aqueous IL solutions decreases with increasing IL concentration (salting-out effect). We observed positive values of ΔGtr′ for Gly, Gly 2, and c(GG) from water to ILs, indicating that the interactions between ILs and protein surface are unfavourable, which leads to stabilization of the native structure of amino acids. Moreover, our experimental data is used to determine transfer free energies (Δgtr′) of the peptide backbone unit (-CH 2CONH-) from water to IL solutions. These results explicitly elucidate that all alkyl ammonium ILs acted as stabilizers for tested model compounds through the exclusion of ILs from surface of model compounds and also reflect the effect of alkyl chain on the stability of protein model compounds. To obtain the mechanism events of the ILs role in enhancing the stability of the model compounds structure, we further studied the UV-vis spectrum analysis. © 2011 Elsevier Ltd. All rights reserved.


PubMed | Sri Padmavathi Womens Degree and Post Graduate College
Type: Journal Article | Journal: The journal of physical chemistry. B | Year: 2012

Mixing of ionic liquids (ILs) with molecular solvent can expand the range of structural properties and the scope of molecular interactions between the molecules of the solvents. Exploiting of these phenomena essentially require a basic fundamental understanding of mixing behavior of ILs with molecular solvents. In this context, a series of protic ILs possessing tetra-alkyl ammonium cation [R(4)N](+) with commonly used anion hydroxide [OH](-) were synthesized and characterized by temperature dependent thermophysical properties. The ILs [R(4)N](+)[OH](-) are varying only in the length of alkyl chain (R is methyl, ethyl, propyl, or butyl) of tetra-alkyl ammonium on the cationic part. The ILs used for the present study included tetramethyl ammonium hydroxide [(CH(3))(4)N](+)[OH](-) (TMAH), tetraethyl ammonium hydroxide [(C(2)H(5))(4)N](+)[OH](-) (TEAH), tetrapropyl ammonium hydroxide [(C(3)H(7))(4)N](+)[OH](-) (TPAH) and tetrabutyl ammonium hydroxide [(C(4)H(9))(4)N](+)[OH](-) (TBAH). The alkyl chain length effect has been analyzed by precise measurements such as densities (), ultrasonic sound velocity (u), and viscosity () of these ILs with polar solvent, N-methyl-2-pyrrolidone (NMP), over the full composition range as a function of temperature. The excess molar volume (V(E)), the deviation in isentropic compressibility ((s)) and deviation in viscosity () were predicted using these properties as a function of the concentration of ILs. Redlich-Kister polynomial was used to correlate the results. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding between ILs and NMP molecules. Later, the hydrogen bonding features between ILs and NMP were also analyzed using a molecular modeling program with the help of HyperChem 7.

Loading Sri Padmavathi Womens Degree and Post Graduate College collaborators
Loading Sri Padmavathi Womens Degree and Post Graduate College collaborators